« AnteriorContinuar »
place it on a stone previously heated, | solution, and fire it at a strong enamel. and when the mixture begins to be in an ling heat, by which it will acquire a eliquated state, stir it well with a shining steel-colour lustre; then take palette knife, and keep adding more oil the oxide of platina mixed up with water by a little at a time, until with the to a thickish consistence, and lay it on continuance of a gentle heat it assumes the steel lustre, and fire it again in a the colour of balsam of sulphur, then kiln or muffle, but not to exceed a bloodadd, with a less degree of heat, tur- / red heat; it is then called silver lustre, pentine in small quantities. 1 oz. of being less resplendent, having more the precipitate of gold will make about solidity and whiteness, and a very similar 1 lb., more or less, of lustre, having appearance to silver. On all white more solidity and opacity than the gold earthenware the platina in solution is lustre. The proportions of the fat oil of perfectly sufficient to produce a silver turpentine to the spirits of turpentine, lustre. are 1 part of the former to 3 of the Bronze Gold.—2 parts, burnish latter.
gold; 2, oxide of copper; 1, quicksilver; SILVER or STEEL LUSTRE.—This is , gold Aux. - Having dissolved the copprepared by taking platina and dissolving per in aqua fortis, it is again separated it in aqua regia composed of equal parts from its solvent and falls to the bottom of spirits of nitre and marine acid. The of the vessel by the addition of iron ; solution must be placed in a sand bath, the precipitate of copper may be inat a moderate temperature; then take creased or diminished at discretion, which 3 parts of the spirits of tar, and 1 part of makes the bronze richer or poorer in the solution of platina, mixing the solu- colour according to the proportion of tion with the tar very gradually, for as burnish gold contained in the mixture. soon as the combination takes place, an It is chiefly used for ornamenting the effervescence will arise, the nitrous acid handles and heads of jars, vases, and so will evaporate and leave the platina in on, and occasionally intermixed with combination with the tar. After the burnish gold. above process has been performed, should Solution of Gold.-Put 40 dwts. the menstruum be found too thin and of aqua regia in a small bottle, to which incapable of using, set it on a sand bath add 5 dwts. of grain gold, the solution as before for a few hours; the spirit of will immediately commence, and may the tar will evaporate, and by that be observed by the effervescence which means a proper consistence will be arises at the time; when the solution is obtained. It must be used with spirits complete, the whole of the gold will be of tar.
dissolved, which will be accomplished in Oxide of Platina. - Dissolve about two hours if the acids be genuine, platina as for silver lustre. Let the but when they are not, it will be resolution fall into a large vessel of water quisite to apply heat to assist in faciliat the temperature of blood-heat ; the tating the solution. sal ammoniac must then be added, and Solution and Oxide of Silver. the precipitate will immediately descend -1 part of nitric acid, and 3 parts of to the bottom of the vessel in an orange- boiling water ; add one-third of its colour powder; decant off the water, and weight of silver, dilute with five times repeatedly apply to the precipitate its quantity of water, then add a portion boiling water until the water becomes of common salt, stirring it all the time quite insipid ; after being gradually and immediately a white precipitate will dried it is then used for the purpose of fall to the bottom of the vessel ; the producing a silver lustre in the follow- liquor must then be decanted off and ing manner :- First, procure brown boiling water repeatedly added, until earthenware of a full soft glaze, and the water is quite insipid. This prewith a broad camel-hair pencil lay on cipitate is the pure oxide of silver, and all over the piece of ware the platina in | is the same as that used in the preparibtion of burnished gold and in staining | the different particles is sufficiently deof glass.
stroyed. This operation will be complete Šolution of Tin.—2 parts of in about ten hours, the weight of the reuitrous acid, and 1 part of muriatic gulus being from 31 to 33 lbs.; on examinacid, with an equal part of water; adding the scoria, if there remains mixed granulated tin by small pieces at a time, with it small pieces of metal like small so that one piece be dissolved before the shot, or when pounded, if the scoria has next is added. This aqua regia will dis | a bluish cast, the fire has not been strong solve half its weight of tin; the solution enough; there is but little danger to be when properly obtained is of a reddish apprehended from the most intense heat, brown or amber colour, but when gela provided the particles in fusion do not tinous the solution is defective.
perforate the crucibles. At the bottom Oxide of Tin.—Take any given of each cake of regulus there will be quantity of grain tin, and granulate it by bismuth slightly adhering, which is melting the tin in an iron ladle; when in | easily separated without the application fusion pour it into a vessel full of cold of any great degree of heat, by placing water, by which means the tin will be the cakes upon an iron plate or pan, reduced into small grains or particles ad which will soon bring the bismuth into hering to each other; then take a biscuit a state of liquefaction, and it can then be dish previously lined with flint, spread it separated from the regulus. slightly over with pounded nitre, take the | TO REFINE REGULUS OF ZAFFRE.— granulated tin, and lay it on the dish 50 parts, l'egulus of zaffre; 6, potash ; 2 inches in thickness, adding a little more 3, sand; pulverize and well mix, then nitre on the top; 1 lb. of nitre will be put in crucibles holding about 1} lb. sufficient to oxidate 5 lbs. of granulated each, and fire in a reverberatory furtin; the dish containing the tin and nitre nace, commencing with a slow fire and is to be calcined in a reverberatory fur gradually increase the heat for about nace or glazing oven; particular atten eight hours; by that time the regulus tion is required in seating it, so that will have fallen to the bottom of the plenty of room remains to admit a free crucible, and the scoria found at the top access of air to pass over the metal, other will be of a blackish green; it will then wise it is impossible to obtain the whole be necessary that another course of of it in an oxidated state.
refining should take place, in order that Balsam of Sulphur. — Take the regulus may be obtained in a more 2 parts of flour of sulphur, and 4 parts perfect state of purity. of turpentine; put them in a vessel over Blue Calx. - 1. 30 parts, refined a slow fire until the sulphur is com regulus of zaffre; 1, plaster; , borax. pletely dissolved; after which add 8 parts 2. 30 parts, refined regulus of cobalt ; of linseed oil, and continue the same 1, plaster; }, borax. These inaterials to degree of heat for about one hour; pre be made very fine, and well mixed ; put vious to becoming cold strain it through the mixture in earthenware biscuit cups a piece of cloth.
1} in. high, 3 in. in diameter, and 1in. Regulus of Zaffre.-112 parts, thick, filled nearly to the top; set them zaffre ; 57, potash ; 181, charcoal. The in a furnace, the fire to be increased charcoal being pulverized, and all the until the mixture is in a state of fusion, materials mixed up together, they are the same degree of heat must be conput into large-sized crucibles capable of tinued for about six hours afterwards, holding from 3 to 4 quarts, and filled and then the fire hastily slackened ; this quite full, then placed in a strong brick- operation will occupy from twelve to built reverberatory furnace, commencing | thirteen hours; at the top of the cups with a slow fire, and continued for some will be found a blue calx separated from time, but as soon as it is heated to a red- | the nickel; but as a large proportion heat, it will require a considerably of blue will still remain in the nickel stronger fire before the cohesion between when sunk to the bottom of the cups,
it will be necessary, in order to pro- | support of the fire must enter at these cure the whole of the blue contained, to doors. On the upper part of the cave pursue precisely the same method over is placed a grate D, to support the fire. again.
The ashes pass through this grate and Cobalt Blue, or Regulus of fall into a tank of water B. Around Cobalt. — 60 parts, cobalt ore; 50, this grate pillars are constructed, which, potash ; 25, sand; 10, charcoal. Work being hollow, serve as flues F F. Resting the same way as for regulus of zaffre. upon these pillars is an iron dome G, and
To REFINE REGULUS OF COBALT. on this is built the principal chimney H. 50 parts, regulus of cobalt ; 6, potash. | Between these pillars are placed the Refine as for regulus of zaffre; the pots E E, which, from the peculiar conoperation of refining must be repeated struction of the furnace, receive the heat until the scoria is of a bright colour and equally on all sides; for, as the flame of a slight bluish hue; then spread the ascends it strikes the dome, and is reverpurified metal, finely pulverized, half an berated, taking the direction pointed out inch thick, on flat pieces of earthenware by the arrows. The pots are constructed covered with Alint; place in a rever- in the form of a cylinder, with a nemiberatory furnace, and apply a moderate spherical top, having a small aperture degree of heat for a few hours.
on one side for the admission of the Glass Making.–The furnace in materials, and their removal when which glass is made is a large circular formed into glass. When the pots are building capable of holding about six placed in the furnace, they are so pots or vessels, in which the glass is arranged that their openings are on the melted. Fig. 1 is an ordinary arrange outside of the fire; they are then built
in by a temporary wall, except the Fig. 1.
orifices, so that no dust or smoke can enter so as to injure the glass. The materials for these various kinds of glass are placed in the pots, and exposed to the heat of the furnace for upwards of forty-eight hours, during one-half of which time the heat is gradually increased, and during the other half gradually decreased, until the metal, as the workmen term the glass, is in a fit state for working. During the time the materials are in the pot, the workman takes out a portion, from time to time, on an iron rod, and examines it when cold, to see whether it is free from air bubbles and of good colour. If the materials employed be very impure, there rises to the surface a scum, which is called sandiver or glass gall, and which resembles large flakes of snow.
FLINT GLASS is employed for making lenses, decanters, drinking glasses, anii
owes its capability of being thus easily ment of this furnace. It is built upon fashioned to the lead contained in it. an arch, and the space underneath, in | The following quantities form a very cluded within the arch, is called the excellent glass :-Fine white sand, 300 cave, as at A. This apartment can be parts; red-lead, or litharge, 200; reclosed by the doors C C, to regulate the fined pearlashes, 80; nitre, 20; arsenig draught, as all the air necessary for the I and manganese, a smaller quantity.
CROWN Glass is a compound of silica, | night, then cooled very gradually. Used potash or soda, and lime. It is employed to imitate the diamond. Other precious as a window glass, and contains no lead. stones are imitated by adding to the The proportions for its formation are-| strass the metallic oxides, as iu colours Fine white sand, 100 parts ; carbonate for glass. of lime, 12; carbonate of sodi, 50; I SOLUBLE or WATER GLASS.—Mix well clippings of crown glass, 100.
200 grains of fine sand, and 600 of fine BOTTLE or GREEN GLASS is made of carbonate of potassa; fuse in a crucible the commonest materials, in about the capable of holding four times as much. following proportions:-Sand, 100 parts; Carbonic acid escapes; the silica and kelp, or impure soda, 30, wood ashes, potassa combine and form glass. Pour 40; potter's clay, 100; cullet, or broken out the glass, which i: commonly termed glass, 100.
silicated potassa, on an iron plate. The PLATE GLASS.—Great care is required compound formed in this manner is pure in the choice of materials, and the silica soap. management of the process for this glass. HARD GLASS FOR RECEIVING COLOUR. The following proportions are used : - Best sand, cleaused by washing, 12 lbs.; Finest white sand, 720 parts; best soda, pearlashes, or fixed alkaline salt purified 450; lime, 80; nitre, 25; cullet, or with nitre, 7 lbs.; saltpetre, 1 lb.; and broken plate glass, 425.
borax, 1 lb The sand being first reduced COMMON WINDOW GLASS.—100 parts, to powder in a mortar, the other insand; 35, chalk; 35, soda-ash, and a gredients should be put to it, and the considerable quantity of broken glass or whole well mixed by pounding them cullet.
together. COLOURS FOR GLASS.–Oxide of gold is Glazing Windows.-Crown glass employed to impart to glass a beautiful is made in circular disks blown by hand; ruby colour. Sub-oxide of copper gives these disks are about 4 ft. diameter, and a red colour. Silver, in all states of the glass averages about in. thick. oxidation, gives a variety of beautiful Owing to the mode of manufacture there yellow and orange colours to glass. is a thick boss in the centre, and the Antimony, lead, and silver, in combi- glass is throughout more or less striated Dation, are employed to produce the or channeled in concentric rings, freinterior yellow colour. The oxides of quently curved in surface, and thicker iron give to glass various shades of green, at the circumference of the disk. Conyellow, red, and black. Oxide of chro- sequently in cutting rectangular panes mium gives a fine green, and oxide of out of a disk there is a considerable loss, cobalt a splendid blue. The colour most or at least variety in quality: one disk valued, next to that produced by gold, will yield about 10 sq. ft. of good window is the yellow comm'inicated by oxide of glass, and the largest pane that can be uranium, and which has an appearance cat from an ordinary disk is about resembling shot silk. White glass or 34 x 22 in. The qualities are classified enamel is made by adding either arsenic into seconds, thirds, and fourths. or the oxide of tin to the melted metal. ! Shect glass is also blown by hand, but The various metals employed in coloure into hollow cylinders about 4 ft. long ing glass are also used in the manu and 10 in. diameter, which are cut off facture of artificial gems, and by their and cut open longitudinally while hot, means the colour and general appearance and therefore fall into flat sheets. A are well imitated.
more perfect window glass can be made STRASS. — Pure caustic potash, 16 by this process, and thicker, and capable parts; white-lead, 85; boracic acid, 41; of yielding larger panes with less waste. arsenious acid, 1 ; finest white sand, 50. Ordinary sheet glass will cut to a pane These materials are carefully selected, of 40 x 30 in., and some to 50 x 36 in. placed in a Hessian crucible and fused It can be made in thicknesses from to in. in a porcelain furnace for a day and a to i in.
Plate glass is cast on a flat table and Glass Painting and Staining. rolled into a sheet of given size and — The different compounds for painting chickness by a massive metal roller. In glass are glasses of easy fusion, chiefly this form, when cool, it is rough plate. coloured with metallic oxides ground,
Ribbed plate is made by using a roller and laid on the glass with spirits of with grooves on its surface. Rough and turpentine. In the production and modiribbed plate are frequently made of fication of glass colours much depends commoner and coarser materials than on the different preparations of the polished plate, being intended for use in | metals, on the small proportion of the factories and warehouses.
metallic oxides employed in proportion Polished plate is rough plate composed to the vitreous mass, on the degree of of good material and afterwards polished fire and time of its continuance, and on on both sides, which is done by rubbing the purity of each ingredient intended two plates together with emery and for vitreous mixtures; from hence diffiother powders between them. Plate culties arise which even a skilful operator glass can be obtained of almost any cannot always remove, and which often thickness from } in. up to 1 in. thick, | frustrate his intention. Having made and of any size up to about 12 x 6 ft. choice of the subject to be painted, cor
In the glazing of a window the sizes of rectly draw the same on a paper exactly the panes, that is to say, the intervals the size intended to be on the glass, of the sash-bars, should be arranged, if | then place the different pieces in regular practicable, to suit the sizes of panes order on the drawing and trace the outof glass which can conveniently be lines therefrom on the glass; when the obtained, so as to avoid waste in cutting; tracing is quite dry the ground colours this consideration is of more consequence may be washed in together with the in using crown and sheet glass than with dark and prominent shades, and also the plate glass. The woodwork of the sash stains required. The stains are laid on should receive its priming coat before in various thicknesses, according to the glazing, the other coats should be put depth of colour required, and when they on afterwards. With crown glass, which are dry the glass is ready to be burned is sometimes curved, it is usual to place in a mume or kiln constructed for the the panes with the convexity outwards. purpose. The panes of glass are laid on When the glazier has fitted the pane to sheets of iron, or earthenware bats, the the opening with his diamond, the re size of the glass, previously spread over bate of the sash-bar facing the outside of with dried ground flin', to prevent the the window, he spreads a thin layer of surface of the glass from being defaced. putty on the face of the rebate and then | After the first burning the stain is presses the glass against it into its place, washed off with warm water, which will and holding it there, spreads a layer of bring to view every part of the subject, putty all round the side of the rebate, in fact, every shade according to the covering the edge of the glass nearly as thickness of colour applied ; to heighten far as the face of the rebate extends on the colour paint on each side of the glass, the inner side of the glass, and bevelling and burn it a second time. The glass off the putty to the outer edge of the will require from four to six firings, the rebate. The putty is then sufficient to exact number of firings depending on hold the pane in its place, and hardens the subject, the degree of perfection in a few days. The glass should not required, and the manner of execution ; touch the sash-bar in any part, on account but after each burning, the pieces of of the danger of its being cracked from glass will want less labour, some of the any unusual pressure; there should be a colours and stains being perfect at the layer of putty all round the edges. This first and second burning, and few require precaution is especially necessary in the utmost quantity. The proper degree glazing windows with iron or stone of heat to which the glass must be nullions or bars.
exposed in the muffle is ascertained by